This is a great basic carabiner. It's my go-to carabiner for belaying. I have the screwgate variety and the screw has never jammed. The red marking on the gate is a convenient immediate indicator that the biner is not locked (if you see red) or locked (no read). I use it with the Black Diamond ATC Guide and it works perfectly. There would be enough room at the top of the biner to have dual ropes through the belay, but I've never used it with two ropes.